1. Field of the Invention
This invention relates to microprocessors, and more particularly, testing and debugging microprocessors.
2. Description of the Related Art
During design and manufacturing of microprocessors, testing and debug are required to both verify the design, and later, to ensure the quality of the finished product. A wide variety of systems and methods for testing and debugging microprocessors are available. In some systems, microprocessors may be tested by operating them synchronously with another processor. In such systems, the other microprocessor is a reference microprocessor that is commonly referred to as a “gold” microprocessor. Testing in such a system includes comparisons of microprocessor circuit outputs that represent the critical internal state of the gold microprocessor and the device under test (DUT).
During this type of testing, it is critical that synchronization between the gold microprocessor and the DUT is maintained. If synchronization is not maintained, any comparisons between the internal states will be invalid. However, maintaining synchronization between the processors is often times very difficult, particularly in a testing environment. Furthermore, it is also critical that the internal state of the microprocessors involve be observable without disturbance. Should the state of either microprocessor (the gold or the DUT) be disturbed during observation, comparisons of data extracted from the two may be invalid.
Another problem is efficiently comparing the data to quickly determine what differences (if any) are present between the gold processor and the DUT.